1. Field of the Invention
The present invention relates generally to an apparatus for loading and unloading semiconductor device packages. More particularly, it relates to an apparatus for loading and unloading semiconductor device packages using servo motors, which apparatus loads the packages into a burn-in board where burn-in tests of the packages are performed, and unloads the tested packages from the burn-in board.
2. Description of the Related Arts
In general, a semiconductor device package is subjected to various reliability tests. The tests include an electrical characteristics test and a burn-in test; the former is performed to check the normal operations and possible failures by connecting all the input/output terminals of the package to a test signal generating circuit, and the latter is performed to check the lifetime and possible defects of the chip in the package by connecting power source terminals and some input/output terminals of the package to a test signal generating circuit and applying an elevated temperature, current and voltage to stress the package.
After completing the assembly process the semiconductor device package is usually loaded into a burn-in socket of a burn-in board and then fed into a burn-in apparatus where the burn-in test is carried out. After the test is performed, the tested package is unloaded from the burn-in socket and sorted depending on the test results. For loading and unloading the package, a loading and unloading apparatus having a plurality of driving tools is usually employed.
The conventional loading and unloading apparatus has a loading tool, a DC test contact tool, an insertion tool, a removal tool, and an extension tool. Each tool is linked to a cam to render its movements in a vertical or horizontal direction.
FIG. 1 is a schematic view of a conventional apparatus for loading and unloading a semiconductor device package from a tube-type container. FIG. 2 is a flow chart showing the steps of loading and unloading the semiconductor device package using the apparatus shown in FIG. 1.
With reference to FIG. 1, the conventional loading and unloading apparatus 100, which is employed for loading and unloading a semiconductor device package into and from a tube-type container (`tube`), consists of three stations: a transferring station, a loading and unloading station, and a sorting station. In the transferring station, a first semiconductor device package 40a (which has not yet been tested in the DC (Direct Current) test and is hereinafter referred to as simply `first semiconductor device package` or `first package`) is transferred to DC test position 45 where the DC test is performed. In the loading and unloading station, the package 40a that completed the DC test is loaded into a burn-in board 47 on an XY table 42, and at the same time a second semiconductor device package 40b, (which has completed its burn-in test and is hereinafter referred to as simply `second semiconductor device package` or `second package`), is unloaded from burn-in board 47 and transferred to receiving position 49. In the sorting station, the second package 40b in receiving position 49 is sorted depending on the test results; those second packages deemed to be good are numbered 40d and those deemed to be defective are numbered 40c.
In more detail, the transferring station comprises a ready position 41 which receives a first semiconductor device package 40a before the DC test. The package free falls from a feed tube 10a onto a transfer rail 32 along which the package moves. The transferring station further comprises a loading tool 21 for transferring the package 40a from the ready position 41 to the centering position 43, and a DC test contact tool 23 for transferring the package 40a from the centering position 43 to a DC test position 45. The loading tool 21 also serves to align the first package 40a with the DC test socket provided at DC test position 45 before transferring the package 40a to centering position 43.
The loading and unloading station, which is located between DC test position 45 and receiving position 49, comprises XY table 42 provided with burn-in board 47 having a burn-in socket, said socket being loaded with a second semiconductor device package 40b to be tested. After the burn-in test, removal tool 27 transfers the second package 40b from the burn-in socket to receiving position 49. Insertion tool 25 loads the first package 40a, which has completed its DC test, from DC test position 45 into the burn-in socket. The insertion tool 25 and removal tool 27 move in the same direction. Thus, when insertion tool 25 picks up first package 40a from DC test position 45, removal tool 27 also picks up second package 40b from burn-in board 47 at the same time. Moreover, insertion tool 25 carrying first package 40a moves toward burn-in board 47, while removal tool 27 carrying second package 40b moves toward receiving position 49 in the same direction. Insertion tool 25 loads first package 40a into the burn-in socket in burn-in board 47, while at the same time removal tool 27 loads second package 40b into receiving position 49. In FIG. 1 and FIG. 3, all the packages 40a, 40b, 40c and 40d are presumed to be moved from the left to the right.
The sorting station has a pusher (not shown) for pushing second package 40b along transfer rail 34 into receiving tube 10b if the package is classified as a good one depending on the burn-in test results. The sorting station also has sorting position 50 which comprises extension tool 29 for transferring second package 40b from receiving position 49 to turntable 51, if the transferred package 40c is considered to be defective. Sorting robot 53 classifies the package 40c depending on the kind and degree of defect.
DC test contact tool 23, insertion tool 25 and removal tool 27 operate together, while loading tool 21 and extension tool 29 work independently depending on the positions of ready position 41 and of turntable 51. Nevertheless, the vertical movements of loading tool 21 and of extension tool 29 are uniformly driven by a cam (not shown).
The steps of loading a first semiconductor device package to a burn-in board using the apparatus 100 described in above, and the steps of sorting a second semiconductor device package after a burn-in test will be described with reference to FIGS. 1 and 2. In preparation step 1 a tube-type container 10a having first semiconductor device packages 40a (before DC test) is provided, and burn-in board 47 having a burn-in socket loaded with second semiconductor device package 40b (after burn-in test) is provided on XY table 42. In transfer step 2, first package 40a is transferred to ready position 41 by freely falling, due to gravity, on a transfer rail 32. In centering step 3, first package 40a is centered, and in DC test step 4, the electrical properties of first package 40a are tested.
If the first package fails the DC test, it is then fed to collection step 5. On the other hand, in loading and unloading step 6, if the first package passes the DC test, it is loaded into the burn-in socket, while at the same time the second package 40b that has already been burn-in tested is unloaded from the burn-in socket. The first package 40a which failed its DC test is immediately returned to preparation step 1 for retesting.
The second package 40b which is unloaded from the burn-in socket in loading and unloading step 6 is transferred to receiving position 49. The second package 40b is moved to receiving step 9 if it is considered good based on the test results, while it is moved to sorting step 8 if considered defective.
The time for one cycle from the loading of a first package into the burn-in socket to the unloading of a second package from the burn-in socket is about 1.5 seconds. However, if any defective first package is found after the DC test is performed, the steps of preparation, transferring, centering and DC test must be repeated, consequently resulting in a decrease in the yield.
FIG. 3 is a schematic view of a conventional apparatus for loading and unloading a semiconductor device package from a tray-type container (`tray`). FIG. 4 is a flow chart showing the steps of loading and unloading the semiconductor device package using the apparatus shown in FIG. 3.
With reference to FIG. 3, loading and unloading apparatus 200, which is employed for loading and unloading a semiconductor device package into and from a tray, consists of three stations: a transferring station, a loading and unloading station, and a sorting station. In the transferring station, the first semiconductor device package 40a is transferred to DC test position 45 where DC testing of the package is performed. In the loading and unloading station, the first package 40a that completed the DC test is loaded into a burn-in board 47 on an XY table 42, and at the same time a second semiconductor device package 40b that has already been burn-in tested is unloaded from the burn-in board 47 and transferred to receiving position 49. In the sorting station, the second package 40b in the receiving position 49 is sorted depending on the burn-in test results.
Unlike loading and unloading apparatus 100 in FIG. 1, the transferring part of the loading and unloading apparatus 200 suitable for the tray does not comprise a ready position 41 since loading tool 21 for the apparatus 200 directly moves first package 40a from feed tray 35 to centering position 43. The feed tray 35 is provided near centering position 43 by using a separate tray transfer apparatus 36, while the receiving tray 37, which receives the good second package 40d, is provided near receiving position 49 by using separate tray transfer apparatus 38.
Extension tool 29, like the extension tool of the apparatus 100 in FIG. 1, transfers second package 40c, which is considered defective based on the burn-in test results, to turntable 51 as well as loads second package 40d, which is considered good, into receiving tray 37.
The steps of loading a first package into the burn-in board by using the apparatus 200 described above, and the steps of sorting a second package after burn-in test will be described with reference to FIGS. 3 and 4. In a preparation step 1 a feed tray 35 having first semiconductor device packages 40a is provided, and burn-in board 47 having a burn-in socket loaded with second semiconductor device package 40b after the burn-in test is provided on XY table 42. In centering step 2, loading tool 21 moves first package 40a from feed tray 35 to centering position 43.
The subsequent DC test step 4, collection step 5, loading and unloading step 6 and sorting step 8 are carried out in the same manner as those in FIG. 2, except for receiving step 9 where the second package 40b, if it is considered good, is transferred to receiving tray 37 by extension tool 29. The time for one cycle from the loading of a first package into the burn-in socket to the unloading of a second package from the burn-in socket is about 1.8 seconds.
The structure of cams 73, 74, 75, 76, 77 and 78 of the loading and unloading apparatus 100, 200 will be described hereinafter.
FIG. 5 is a schematic side view of a cam for driving tools of the apparatuses in FIG. 1 and FIG. 3; FIG. 6 is a front view of a cam for moving the tools of the apparatuses in FIG. 1 and FIG. 3 in a vertical direction; and FIG. 7 is a front view of a cam for moving the tools of the apparatuses in FIG. 1 and FIG. 3 in a horizontal direction.
With reference to FIG. 5, a plurality of cams, i.e. first 73, second 74, third 75, fourth 76, fifth 77 and sixth cams 78 are fastened to one shaft 71. The individual cams are spaced from each other. Each cam has a respective corresponding link 52a, 52b, 52c, 52d, 52e or 52f. Each link has a bearing 56, which is in contact with the outer surface of the cam. Therefore, cams 73, 74, 75, 76, 77 and 78 rotate in the same direction as the rotation of shaft 71, while links 52a-f move reciprocally in the vertical direction.
Third 75, fourth 76 and fifth cams 77 drive DC test contact tool 23, insertion tool 25 and removal tool 27, respectively, in the vertical direction.
Second cam 74 is coupled to the loading tool 21, and sixth cam 78 is coupled to the extension tool 29. First cam 73 simultaneously moves DC test contact tool 23, insertion tool 25 and removal tool 27 in the horizontal direction. The structure of the coupling of removal tool 27 to fifth cam 77 and the structure of first cam 73 are schematically shown in FIG. 5.
With reference to FIGS. 5 and 6, removal tool 27 is moved vertically by the action of fifth cam 77. In more detail, removal tool 27 moves vertically by the motion of fifth cam 77 as well as by the action of air cylinder 50e mechanically coupled to fifth cam 77.
Fifth cam 77 and air cylinder 50e are coupled to removal tool 27 so that one end of air cylinder 50e is fixed to the body of loading and unloading apparatus 200. Thus, cylinder shaft 53e is inserted and fitted into cylinder fixing part 5 le of air cylinder 50e so as to be fixed to the body of loading and unloading apparatus 200. Cylinder rod 57e extending from the other end of air cylinder 50e is coupled to one end of fifth link 52e by means of fixing projection 59e.
Use of the term "fitted" indicates that one member is fitted into the other member in such a way that the two members are fastened together, while one member can still freely rotate or move relative to the other member.
Fifth link 52e may have a T-shape, and is coupled to air cylinder 50e and fifth cam 77 at its horizontal ends. Thus, air cylinder 50e is coupled substantially perpendicular to one horizontal end of fifth link 52e by means of fixing protrusion 59e. The outer surface of fifth cam 77 is in contact with bearing 56e provided at the other horizontal end of fifth link 50e. The remaining end of fifth link 52e is coupled to one end of fifth link rod 61e by means of fixing protrusion 58e. Hinge shaft 54e is inserted into the center hole of fifth link 52e so that fifth link 52e can rotate about hinge shaft 54e. Fifth cam 77 is fit onto cam shaft 71.
The other end of fifth link rod 61e is coupled to one end of fifth rotation link aria 60e. Fifth rotation link 60e may have an L-shape, and its one end is coupled to one end of fifth link rod 61e while its other end is coupled to transfer guide 82 of removal tool 27 by fixing means 85. Hinge shaft 63e is provided in a corner of fifth rotation link 60e such that fifth rotation link 60e can rotate about shaft 63e.
Removal tool 27 is equipped with transfer guide 82 coupled to one end of fifth rotation link 60e by means of fixing means 85; tool head 86 spaced from transfer guide 82; transfer rod 83 fitted between and into transfer guide 82 and tool head 86; transfer rod guides 84 placed at opposite sides of transfer rod 83 and fitted between transfer guide 82 and tool head 86; and rotation means 81 such as a rotary actuator coupled to one end of transfer rod 83 at an upper position of transfer guide 82. Suction means 87 for picking up a semiconductor device package is provided at the other end of transfer rod 83, the other end extending downward toward tool head 86. Fixing means 85, which may have a ball shape, can freely rotate in and move along trench groove 89 in transfer guide 82. Rotation means 81 is provided at transfer rod 83 in order to facilitate the positioning of a semiconductor device package picked up by suction means 87 by using rotation means 81.
Removal tool 27 is moved in the vertical direction responsive to movement of fifth cam 77 as follows: when fifth cam 77 rotates by the rotation of cam shaft 71, fifth link rod 61 e coupled to fifth link 52e moves leftward and fifth rotation link 60e coupled to fifth link rod 61e rotates counter-clockwise about hinge shaft 63e, so that transfer guide 82 coupled to fifth rotation link 60e and removal tool 27 move upward. The maximum height which removal tool 27 can reach is the distance from the center of cam shaft 71 to the point where bearing 56e is in contact with the outer surface of fifth cam 77. At this time, fixing ball 85, which couples fifth rotation link 60e to transfer guide 82, moves in the horizontal direction along trench groove 89. Then, once removal tool 27 reaches the maximum height, it goes down by the reverse movement used for going up. At this time, fixing ball 85 moves rightward along trench groove 89. The downward movement of bearing 56e of fifth link 52e is accomplished by the motion of fifth cam 77. By contrast, the lifting of bearing 56e of fifth link 52e, which is at its lowest position, requires the motion of air cylinder 50e. Thus, bearing 56e of fifth link goes up while staying in contact with fifth cam 77 by the downward motion of cylinder rod 57e of air cylinder 50e.
Thus, the upward motion of removal tool 27 is accomplished by the motion of fifth cam 77, while downward motion of remove remove tool 27 is accomplished by the motion of air cylinder 50e.
With reference to FIGS. 5 and 7, the structure in which DC test contact tool 23, insertion tool 25 and removal tool 27 are coupled to first cam 73 will be described. One end of air cylinder 50a for rotating first link 52a counter-clockwise is fastened to the body of the loading and unloading apparatus. In more detail, cylinder shaft 53a is inserted into fixing part 51a of air cylinder 50a so that air cylinder 50a can be coupled to the loading and unloading apparatus. Cylinder rod 57a extending from the other end of air cylinder 50a is coupled to one end of first link 52a by means of fixing protrusion 59a.
Hinge shaft 54a is inserted and fitted into a center hole of first link 52a, and one end of first link 52a is coupled to one end of first link rod 61a by means of fixing protrusion 58a. Bearing 56a is coupled between hinge shaft 54a of first link 52a and fixing protrusion 58a coupled to first link rod 61a, and located so as to be in contact with an outer surface of first cam 73.
The other end of first link rod 61 a is coupled to one end of first rotation link 60a by means of fixing protrusion 62a.
First rotation link 60a may have an L-shape as does fifth rotation link 60e. One end of first rotation link 60a is coupled to one end of first link rod 61a, and the other end thereof is coupled to one end of coupling rod 65a by means of fixing protrusion 64a. Hinge shaft 63a is provided in the corner of first rotation link 60a such that first rotation link 60a can rotate about shaft 63a.
The other end of coupling rod 65a is mechanically coupled to transfer means 93, into which DC test contact tool 23, insertion tool 25 and removal tool 27 are inserted and fitted. In more detail, the other end of coupling rod 65a is coupled to fixing means 91 of transfer means 93, and fixing means 91 is attached to sliding member 92 of transfer means 93. Fixing means 91 may have a ball shape. Sliding member 92 is located under transfer means 93, and engaged into sliding groove 94 in two opposing transfer rails 90 so that sliding member 92 can freely slide in the rails 90.
Transfer rod 83 and transfer rod guides 84 of removal tool 27, insertion tool 25, and DC test contact tool 23 are engaged to transfer means 93.
DC test contact tool 23, insertion tool 25 and removal tool 27 move in the horizontal direction depending on the movement of first cam 73 as follows: bearing 56a is positioned so that the distance between bearing 56a in contact with the outer surface of first cam 73 and cam shaft 71 is shortest. When cam shaft 71 rotates, the distance between the center of cam shaft 71 and bearing 56a of first link 52a increases, and first link 52a rotates clockwise about hinge shaft 54a. At this time, the portion of first link 52a to the right of hinge shaft 54a moves downward, and first link rod 61a coupled to first link 52a moves downward as well.
First rotation link 60a coupled to first link rod 61a rotates clockwise and transfer means 93 coupled to first rotation link 60a via connection rod 65a moves leftward, so that DC test contact tool 23, insertion tool 25 and removal tool 27, all of which are coupled to transfer means 93, can move leftward.
Then, once transfer means 93 reaches the maximum point of leftward movement, in other words, it reaches the point where the distance between the center of cam shaft 71 and bearing 56a of first link 52a is maximum, transfer means 93 moves rightward to its original position by reverse movement. At this time, the downward movement of bearing 56a of first link 52a is accomplished by the motion of first cam 73. By contrast, the lifting of bearing 56a of first link 52a, which is at its lowest position, requires the motion of air cylinder 50a. Thus, first link 52a rotates counterclockwise about hinge shaft 54a of first link 52a due to the downward motion of cylinder 57a, and the end of first link 52a coupled to first link rod 61a moves up.
Thus, the leftward motion of transfer means 93 is accomplished by the motion of first cam 73, while the rightward motion of transfer means 93 is accomplished by the motion of air cylinder 50a. Of course, the vertical movements of DC test contact tool 23, insertion tool 25 and removal tool 27 are associated with the motions of third 75, fourth 76 and fifth cams 77.
For the loading and unloading apparatus described above, one cycle of cam shaft operation allows the loading or unloading of one semiconductor device package into or from the DC test position or burn-in socket. Thus, simultaneous operations of the DC test contact tool, insertion tool and removal tool as driven by cam 73 are required. The loading tool and the extension tool are not controlled by cam 73. However, their vertical movements are still governed by cam 74 and 78, respectively. Accordingly, the independent movement of each tool is not possible.
Without independent motion of each tool the DC test contact tool has only one opportunity to properly insert the first semiconductor device package into the DC test socket, and if proper insertion is not achieved on the first try, then the first semiconductor device package may be deemed defective and collected for refeeding into a new tube or tray for retesting. However, if independent vertical movement of the DC test tool is allowed, the DC test tool could have a second chance to properly insert the first semiconductor package into the DC test socket, resulting in a time savings by avoiding unnecessary retesting.
Moreover, the cycle time for a cam-driven type apparatus such as the apparatus described above has a finite limit which cannot be further reduced without the addition of at least one cam.
Further, the cycle time of the cam-driven apparatus is long and is governed by the movement of the mechanical elements (i.e., the cams and linkages); independent or reverse movement is not possible; and two or more packages cannot be handled at once.